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Updated: Jun 24, 2025
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DNA-Tethered RNA Polymerase for Programmable In vitro Transcription and Molecular Computation
Published on: December 29, 2021
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Assembly of the Tn7 targeting complex by a regulated stepwise process.
Yao Shen1, Shreya S Krishnan1, Michael T Petassi2
1Department of Biochemistry, McGill University, Montreal, QC H3G 0B1, Canada; Centre de recherche en biologie structurale (CRBS), McGill University, Montreal, QC H3G 0B1, Canada.
Molecular Cell
|June 4, 2024
Summary
The Tn7 transposon system uses TnsC and TniQ proteins to precisely insert DNA. Structural studies reveal how ATP binding to TnsC controls its assembly into a ring, ensuring accurate transposition.
Area of Science:
- Molecular Biology
- Structural Biology
- Genetics
Background:
- The Tn7 family of transposons exhibits highly regulated transposition.
- Targeting involves TniQ proteins and the TnsC adaptor to recruit transposase.
- Understanding the mechanism of target selection and DNA integration is crucial.
Purpose of the Study:
- To elucidate the structural basis of TnsC regulation by TniQ during Tn7 transposition.
- To understand the role of ATP/ADP binding in TnsC assembly and function.
- To provide insights into the precise and oriented DNA insertion mechanism of Tn7.
Main Methods:
- Cryoelectron microscopy (cryo-EM) to determine the structures of TnsC bound to the TniQ domain of TnsD.
- Biochemical assays to study the nucleotide-dependent behavior of TnsC.
Main Results:
- Determined cryo-EM structures of TnsC complexed with TniQ domain of TnsD.
- Revealed distinct conformational states of TnsC based on ATP versus ADP binding.
- Showed TnsD acts as an exchange factor, facilitating unidirectional loading of ATP-bound TnsC into a heptameric ring.
- Identified functionally distinct TnsC protomers within the assembled ring.
Conclusions:
- The TnsD-TnsC interaction and nucleotide exchange mechanism ensure unidirectional TnsC ring assembly at target sites.
- Functionally distinct TnsC protomers regulate target immunity and ensure precise, oriented DNA insertion by Tn7 transposons.
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